<!--
 * @Description: 呼吸灯
 * @Author: zzj
 * @Date: 2021-08-19 10:28:07
 * @LastEditors: zzj
 * @LastEditTime: 2021-08-19 10:59:13
-->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>呼吸灯</title>
    <style>
        body{
            margin: 0;
            padding: 0;
        }
        div{
            box-sizing: border-box;
        }
        .content{
            width: 400px;
            height: 600px;
            background-color: black;
            margin: 0 auto;
        }

        .content > .box{
            height: 400px;
            padding: 40px;
            animation-name: outer;
            animation-timing-function:linear ;
            animation-duration: 5s;
            animation-iteration-count: infinite;
        }
        .content > .box .circle{
            border-radius: 50%;
        }
        .content > .box > .outer{
            border: 5px solid rgb(163, 162, 154);
            height: 100%;
            padding: 20px;
            animation-name: inner;
            animation-duration: 5s;
            animation-timing-function: linear;
            animation-iteration-count: infinite;
        }
        .content > .box > .outer > .inner{
            border: 10px solid white;
            height: 100%;
        }

        @keyframes outer{
            25%{
                padding: 30px;
            }
            50%{
                padding: 40px;
            }
        }

        @keyframes inner{
            25%{
                padding: 30px;
            }
            50%{
                padding: 20px;
            }
            75%{
                padding: 30px;
            }
            100%{
                padding: 20px;
            }
        }
    </style>
</head>
<body>
    <div class="content">
        <div class="box">
            <div class="outer circle">
                <div class="inner circle">
                </div>
            </div>
        </div>
    </div>
</body>
</html>